1. Field of the Invention
This invention relates to a method of manufacturing magnetron anodes.
2. Description of the Related Art
Conventional magnetron anodes for use in, for example, microwaves ovens, comprise an anode cylinder and a plurality of anode vanes radially extending in the anode cylinder, each adjacent pair defining a resonance cavity. Though these vanes can be made of Cu or Al, both of which are good electric and thermal conductors, they are generally made of Cu as it has high heat resistance.
In the conventional method of manufacturing such a magnetron anode, the anode vanes are united with an anode cylinder, by a solder mainly consisting of Ag, in a furnace filled with H.sub.2 gas or a mixture of H.sub.2 and N.sub.2 gases. Thus, the method requires large equipment for soldering, which increases the cost. Further, a solder is needed for each anode vane, or an annular solder which contacts the inner periphery of the anode cylinder must be prepared. Hence, the resulting product is very expensive.
Moreover, in the method, the anode is assembled by using a jig before soldering, and then soldered in a furnace, together with the jig. To facilitate the assembling of the anode, clearances are provided between the jig and respective components of the anode. These clearances change as the components and the jig inevitably expand when the temperature in the furnace rises to about 800.degree.-930.degree. C. for soldering. Thus, the resulting product has an inner diameter defined by the anode vanes at the cathode side, and an angle defined by each adjacent pair of the vanes, both different from the design values. Consequently, the product cannot but have an oscillation frequency or oscillation mode which is far from stable.
Further, the specification of Japanese Patent Disclosure No. 56-156646 shows a method of welding a anode cylinder and anode vanes by radiating laser beams onto the anode cylinder from the outside. In this method, the anode vanes are secured to the anode cylinder, with their end faces completely melted. Therefore, the anode vanes must be fixed in position during welding, as in the above soldering method, in order to prevent changes in the inner diameter defined by the vanes at the cathode side, and in the angle between each adjacent pair of vanes.